Hydrocracking of heavy oils



Filed April 9. 1951 March 13, 1956 LA VERN H. BECKBERGER HYDROCRACKINGOF' HEAVY OILS MM M Jfzc@ ATTORNEYS United i States Patent OHYDROCRACKING F HEAVY OILS La VernI-I. Beckherger, Markham, Ill.,assigner to Sirlclair Relining Company, New York, N. Y., a corporationof Maine Application April 9, 1951, Serial No. 220,091

6 Claims. (05196-49) My invention relates to a combination fluid cokingand cracking process for converting heavy oils into good yields oflight, low-boiling hydrocarbons. According to my process, a heavy oil, eg. a reduced crude, is charged into a body of coke particle continuouslymaintained in iiuidizedcondition in a coking reaction. The larger cokeparticles which form are selectively removed and contacted with steam ina separate zone for generation of a water gas mixture, which is returnedto the coking reaction as the fiuidizing medium. The overhead from thecoking reaction is admixed with activated coke particles withdrawn fromthe water gas generator to form a uid suspension and the mixture iscracked to gasoline-range products.

In the co-pending application of Kenneth M. Watson, Serial No. 121,575,tiled October l5, 1949, now U. S. Patent 2,707,702, a coking process isdisclosed which has the important advantage of being continuouslyoperable without wall and reactor coking and resultant shutdown.Essentially, the process involves maintaining a bed of relativelyadsorbent coke particles as seed particles in a fluidized state in thereaction zone and charging a hydrocarbon oil therein. The largeparticles built up by coke laydown are selectively and continuouslyremoved from the reaction zone. Selective removal of these large cokeparticles is accomplished by a size classifying or elutriating systemopening directly into the uidized bed of coke particles. The coke formedin the process is selectively deposited on the relatively adsorbent seedparticles and the coke product is selectively withdrawn in the form ofthe larger particles by means of the internal elutriator which retainsthe smaller particles in the bed of seed coke and allows the largerparticles to fall into a transportation and storage system from whichthey are removed as net coke make. As the uidizing medium, steam, fluegases having a low oxygen content or an inert gas such as nitrogen or anaphtha or light refractory gas oil are disclosed. The lightercomponents ofthe charge oil, together with the lighter decompositionproducts and the fluidizing and elutriating media, are taken oftoverhead.

Heavy oils of the nature of residual stocks, e. g. reduced crudes, makepoor charging stocks for catalytic cracking processes. Such oilsordinarily contain compounds which may either temporarily or permanentlypoison the catalyst, e. g., metallic salts, nitrogen-base compounds,sulfur and sulfur-containing compounds. Residual oils also containasphaltenes and fused-ring aromatics which tend toward excessive cokemake. Accordingly, in conventional practice it is practically necessaryto remove such coke-forming constituents prior to cracking with acatalyst by such expedients as fractionation, deasphalting, visbreaking,pitching `or coking.

Thus residual stocks are only susceptible `to catalytic cracking whenspecially pretreated. The fact that clean gas oils are requisite forVcatalytic` cracking processing usually means considerable extra handlingis involved and that operational continuity is poor and this accounts inpart for the relatively higher economic cost of such operations.

I have devised a combination tluid-type process for converting suchheavy oils into good yields of gasolinerange boiling hydrocarbons by acontinuous process wherein the coking operation described above iscarried out in conjunction with a cracking step. According to myinvention, a heavy oil is charged into a body of coke particlesmaintained in fluidized condition in a coking reaction vessel. The largecoke particles which form are selectively removed and are contacted withsteam in a separate Zone in huid-type admixture for the generation of awater gas mixture which is returned to the Coking reaction as thefluidizing medium. The lighter components of the heavy oil charged tothe coking vessel are taking o overhead and are admixed with activatedcoke particles from the water gas generator in amount suflicient toprovide a uid suspension. The uidized admixture of oil and cokeparticles are cracked in a reaction zone at a temperature in the rangeapproximating 900 to 1100 F. for a period of time sufficient to effectreaction into good yields of gasoline range boiling hydrocarbons. Thegasoline and other valuable light products are then separated from theeil-'tuent products of reaction.

l have also found that the overall yield of light, gasoline-rangehydrocarbon products can be further improved by addition of promotingcompounds to the coking and cracking steps. Accordingly, I add thecarbonate of a metal selected from the left hand side of groups l and llof the periodic vtable to accelerate the water gas reaction or I add aninorganic acid to promote the cracking reaction, or both reactions areso promoted. As exemplary of such water gas promoters, there are sodiumcarbonate, potassium carbonate and barium carbonate. Suitable crackingpromoters include hydrochloric acid, boric acid, phosphoric acid,sulfuric acid, hydrouoric acid, hydroiiuosilicic acid, molybdic acid,vanadic acid, chloroplatinic acid and chromic acid. The promoters areadded in small amounts, in quantities up to about 5 per cent by Weighton the reaction mixture.

Thus my invention offers several important advantages.

4Superiicially, heavy oils, e. g. straight-run residual stocks,

which are generally unsuited in such condition for catalytic crackingare eiectively converted to good yields of gasoline-range products. Andsince the coking operation is continuous the entire process may beoperated without interruption or intermittent shutdown. Because theiuidizing gas, i. e. the water gas, contains a high concentration ofhydrogen, the coke forming constituents in the charge oil are in parthydrogenated to lighter products in the coking vessel. Since thehydrogen is present in the coking reaction overhead with the eitluentoil products, additional hydrogenation and suppression of coke formationoccurs further along in the cracking reaction.

The present invention also has the important additional advantage inthat the process produces its own catalyst because the coke particlesprepared are used for the cracking step. By regulation of the cokingreaction through the elutriator the size of such catalyst particles maybe accurately controlled. By contacting steam with the coke particlesfor generation of the water gas mixture, the coke is simultaneouslyactivated and'hence when withdrawn for fluid admixture with the oil tobe cracked, it is specially suited for cracking to good yields of highquality gasoline products. Thus instead of producing mere low cost coke,the coke is instead utilized in large proportions as a valuable, highlyactive catalyst. In addition, when the water gas mixture is injectedinto the coking reactor, it also takes along coke nes. These lines thenact as seed coke for the coking reaction and hence my process alsoproduces its own seed coke.

The process is capable of supplying its own heat requirements. The cokeproduced in excess of water gas generation requirements may be oxidizedto provide such heat requirements. A heat balance is also achieved inthe system between the water gas and the coking reactions. Since the hotwater gas mixture is taken olf at highly elevated temperatures and ispassed to the coking reaction at a somewhat lower temperature,regulation of the oxygen to steam ratio in the water gas generator willserve to etliciently control the temperature therein.

The process according to my invention will be more clearly understood byreference to Figure 1 of the accompanying drawings, which represents asomewhat schematic flow plan of my process.

The essential elements in the system are the uid coking zone,represented by iluid coker 1.5, the water gas generation zone,illustrated by fluid water gas generator 25, and fluid cracking zone,reactor 26. The water gas generator employed is adapted to handling ofthe coke particles while in iluid suspension and the reactor is aconventional fluid-type reactor.

As illustrated in the drawing, a residual stock, e. g. a reduced crude,is charged to the process by line 11. The feed is preheated to atemperature of about 750 F. in fired heater 1.2 and is introduced byline 13 and spray 14 into the coke bed of the fluid coker 15. Tocommence the operation the coke bed is charged with seed coke, forinstance that obtained from a prior run. The size range of the seed cokefor startup should be relatively narrow for ease in iluidization,between about 100 to 200 mesh particles (Tyler). 'In steady stateoperation, however, the size of the coke particles in the fluid cokerwill reach an equilibrium distribution determined by the overall processconditions. Fluidizing water gas at about 1200" F. from hot water gasmanifold 30 is introduced to the bottom of reactor 15 by line 17.Dispersion gas is taken from the same manifold by line 18.

Coke draw-olf is effected through elutriator 19 which opens directlyinto the coke bed through the grid plate 20. Elutriating Water gas isprovided by manifold 30 and is introduced near the bottom of elutriator19 by line 21. The coke make is taken off by Y-connection 22 where itmay be passed to storage receiver 23 by line 24 or to the water gasgenerator 25 by line 25a. The coke removed from the process may be usedas a source of heat, that is, as fuel in the heater. The lightercomponents of the reaction mixture pass overhead by line 27 whichcontains cyclone separator 2S to remove some of the coke particlestherefrom.

Processing conditions in the uid coker may be varied somewhat accordingto the nature of the feed stock. Thus a unit embodying my inventionordinarily charges a heavy oil such as a reduced crude. a cracking stilltar or an asphalt and is run for a maximum yield of clean distillate.Under these conditions l. have found that a coke bed temperature ofabout 800 to 1200" F. is satisfactory. About 900 to 1000 F. isparticularly desirable. To prevent heater and line coking, the heavy oilcharge is heated to about 700 to 800 F. in the presence of water gas ina conventional external furnace or heater coil and is sprayed into thereactor bed. The hot water gas, in addition to preheating the oil,minimizes excessive coke formation because of the hydrogen present.

The coke reactor pressure is advantageously kept relatively low, rangingfrom about atmospheric to about 75 p. s. i. The density of the luidizedcoke bed varies from about 25 to about 50 pounds per cubic foot but isgenerally of the order of about to 40 pounds per cubic foot. Fluidizingwater gas flow lower than about 1 foot per second is suilicient for 100to 200 mesh coke particles. Higher superficial velocities are limited byexcessive carry-over.

The lighter components pass overhead by line 27 and are carried toreactor 26. The coke formed in the reaction required for heat and watergas is transported by steam from line 29 to water gas generator 25. Thesteam is preheated in admixture with oxygen, to about 350 F.

The mixture of steam, oxygen and coke is reacted in the generator andthe water gas resulting is carried by manifold line 30. Cycloneseparator 31 separates out a large portion of the coke fines prior topassage to the manifold lines 30 and 45.

Reaction conditions in the water gas generator may be varied somewhatand depend largely upon the available oxygen. A temperature betweenabout 1200 to 1600 F. is generally employed, advantageously about 1400F. The fines that carry over to the coking reactor serves as acontinuous source of seed particles for the coking reaction. The hotelfuent water gas mixture given off at about 1400o F. providespractically all of the heat for the coking reaction and the actual rateof flow in the lines in and out of the generator are suitably regulatedfor such a heat balance. To minimize inert gas handling through theprocessing stages and to provide a maximum hydrogen partial pressurethroughout, I utilize high purity oxygen in the generator. Generally,oxygen purity at least as high as per cent is necessary to minimize suchinert gas formation. per cent plus pure oxygen may be needed in someinstances to accomplish this. In addition, heat balance is maintained onthe fluid coke and water gas generator by regulating the ratio of oxygento steam in the generator.

The water gas formation is accelerated by the introduction intogenerator 25 of a small amount of sodium carbonate. The sodium carbonateis added from line fr?. as a finely divided solid in admixture withsteam. The metal carbonate promoters are usually added in iinely-dividedform by direct injection into the generator bed by means of the steamline, or addition may be made through the cyclone. The hot cokeparticles in the generator 25 are removed through standpipe 33 andinjected into the oil line 27 from the coker overhead.

The activated coke particles are then mixed with the distillate streamto form a suspension of the uid type, and the mixture is cracked. Thecoke particles are added in considerable excess over the distillateportion, that is, in excess of a coke-oil ratio of 1:1 to as high as30:1 Generally, ratios of about 5:1 to 15:1 are particularlysatisfactory. The size of the coke particles used in the fluidsuspension are regulated back at the coker by appropriate adjustment ofthe elutriating means. Usually, the particle size measure is variedbetween about 50 to mesh ("l`y1er); satisfactory results are providedwhen the size varies between about 5 and 50 per cent on a 100- meshscreen. The density of the reactor bed will vary between about 25 to 35pounds per cubic foot and about 28 to 30 pounds per cubic foot isusually provided. The reaction is carried out at moderate temperaturesin the range approximating 900 to l000 F., advantageously at about 950F. The reaction pressures may be varied bctween about atmospheric to 50p. s. i. g. Advantageously, the reaction is carried out at about 950 F.for a pressure between about l0 to 30 p. s. i. g.

A small amount of hydrochloric acid gas is added by line 3d to promotethe cracking reaction. The acid promotors are usually added as a gas tothe coke as it is taken from the generator or to the coke-oil streamjust prior to entrance into the cracking zone.

The efuent products of reaction are taken off from reactor 26 by line35' after passing through cyclone separators 36 for the separation ofsuspended catalyst matter. rEhe vapors are passed to separator 44 by theline 35. ln the separator 134, the components of the efuent areseparated. The non-condensible or fixed gases are recovered by line 46,the water (as steam) by line 47, the gasolinerange products by line i8and diesel fuel or heating oil by line 49. The heavy oil, boiling aboveabout 650 F., and catalyst remaining therein is taken off as a slurry byline 50 and may be recycled as feed material.

l claim:

l. The combination Huid-type process for coking and cracking a heavy oilwhich comprises introducing the heavy oil into a body of coke particlesmaintained in uidized condition in a coking zone by injection therein ofa water gas mixture, selectively removing large coke particles as formedfrom the coking zone to the substantial exclusion of smaller particlesby size classifying the coke particles by means of an elutriating gaspassing into the Vbody of coke particles and contacting a iiuidsuspension of said large coke particles with steam in a separate zone togenerate a water gas mixture, returning said Water gas mixture to thecoking zone as the uidizing medium, taking off the hydrocarbon overheadfrom the coking zone and admixing same with activated coke particlesfrom the water gas generation zone so as to provide a Huid suspension,cracking said iluid mixture at elevated temperatures in the rangeapproximating 900 to 1100" F. for a time sufficient to produce lightgasolinerange boiling hydrocarbons, and separating said gasolineproducts from the eluent.

2. A process according to claim 1 wherein an inorganic acid is added inamount suicient to promote the cracking reaction.

3. A process according to claim 1 wherein a carbonate of a metalselected from the left hand side of group I and II of the periodic tableis added in amount sufficient to promote the water gas reaction.

4. A process according to claim l wherein the oxygen present in thewater gas generation zone is of suiciently high purity to substantiallyminimize inert gas dilution.4

5. A process according to claim 1 wherein the heavy oil and catalystmatter separated from the etlluent products of reaction are recycled tothe coking zone.

6. A process according to claim 1 wherein hydrocarbon overhead from thecoking zone is admixed with activated coke particles from the water gasgeneration zone so as to provide a uidized mixture, the uidized mixtureis cracked at elevated temperatures in the range approximating 900 to1100 F. for a time sucient to produce light gasoline-range boilinghydrocarbons and said gasoline products are separated from the effluent.

References Cited in the file of this patent UNITED STATES PATENTS2,097,989 Schick et al. Nov. 2, 1937 2,407,052 Bailey et al. Sept. 3,1946 2,416,003 Guyer Feb. 1S, 1947 2,428,715 Marisic Oct. 7, 19472,527,575 Roetheli Oct. 31, 1950 2,600,430 Riblett June 17, 1952

1. THE COMBINATION FLUID-TYPE PROCESS FOR COKING AND CRACKING A HEAVY OIL WHICH COMPRISES INTRODUCING THE HEAVY OIL INTO A BODY OF COKE PARTICLES MAINTAINED IN FLUIDIZED CONDITION IN A COKING ZONE BY INJECTION THEREIN OF A WATER GAS MIXTURE, SELEVTIVELY REMOVING LARGE COKE PARTICLES AS FORMED FROM THE COOKING ZONE TO THE SUBSTANTIAL EXCLUSION OF SMALLER PARTICLES BY SIZE CLASSIFYING THE COKE PARTICLES BY MEANS OF AN ELUTRIATING GAS PASSING INTO THE BODY OF COKE PARTICLES AND CONTACTING A FLUID SUSPENSION OF SAID LARGE COKE PARTICLES WITH STREAM IN A SEPARATE ZONE TO GENERATE A WATER GAS MIXTURE, RETURNING SAID WATER GAS MIXTURE TO THE COKING ZONE AS THE FLUIDIZING MEDIUM, TAKING OFF THE HYDROCARBON OVERHEAD FROM THE COKING ZONE AND ADMIXING SAME WITH ACTIVATED COKE PARTICLES FROM THE WATER GAS GENERATION ZONE SO AS TO PROVIDE A FLUID SUSPENSION, CRACKING SAID FLUID MIXTURE AT ELEVATED TEMEPRATURES IN THE RANGE APPROXIMATING 900* TO 1100* F. FOR A TIME SUFFICIENT TO PRODUCE LIGHT GASOLINERANGE BOILING HYDROCARBONS, AND SEPARATING SAID GASOLINE PRODUCTS FROM THE EFFLUENT. 